Au/ZnO hybrid nanocatalysts impregnated in N-doped graphene for simultaneous determination of ascorbic acid, acetaminophen and dopamine

A novel Au/ZnO/N-doped graphene hybrid nanostructure was synthesized for the electrochemical evaluation of AA, DA and AC. The formation of N-doped graphene uses hydrothermal method with urea as reducing agent and nitrogen source. Moreover, Au nanoparticles deposited on ZnO nanocrystals surface, forming Au/ZnO hybrid nanocatalysts, undergo a super-hydrophobic to superhydrophilic conversion. We present Au/ZnO hybrid nanocatalysts impregnated in N-doped graphene sheets through sonication technique. In comparison to N-doped graphene/GCE, Au/ZnO/N-doped graphene/GCE provides superior performance in terms of peak potential and current in CV and DPV measurements. The observed low oxidation potential and the high oxidation current for AA, DA and AC could be attributed to the synergetic effect between N-doped graphene and Au/ZnO hybrid nanocatalysts, and the small Au nanoparticles located on ZnO nanocrystals can effectively decrease their oxidation and be conducive to the separation of the three species, and may result in higher oxidation currents. The peak separations between AA and DA, DA and AC, and AC and AA are large up to 195, 198 and 393 mV, respectively. The calibration curves for AA, DA and AC were obtained in the range of 30.00-13.00 × 103, 2.00-0.18 × 103 and 5.00-3.10 × 103 μM, respectively. The detection limits (S/N = 3) were 5.00, 0.40 and 0.80 μM for AA, DA and AC, respectively.